1. Field of the Invention
The present invention relates to electrode catalysts for electrochemical systems used in acidic electrolytes in the fields of water electrolysis, organic electrolysis, fuel cells, etc.
2. Related Art
Noble metals, in particular, platinum, are stable at high electrical potentials and have high catalytic activity for various reactions, and thus are used as electrode catalysts for various electrochemical systems. However, because of the high cost and limited reserves of platinum and since electrode catalysts having higher activity are required for fuel cells, alternative materials to platinum catalysts have been desired.
Metal oxynitrides have been developed as photocatalysts that decompose water under visible light (e.g., Non-Patent Document 1 and Patent Document 1). However, there have been no attempts to use metal oxynitrides as electrode catalysts.
Non-Patent Document 1: M. Hara et al., Catal. Today., 78, 555 (2003)
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-205104
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2002-66333
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2002-154823
Patent Document 4: Japanese Unexamined Patent Application Publication No. 2002-321907